ASK TOM WHY.

Dear Tom, Why is it colder in higher elevations (such...

Why is it colder in higher elevations (such as a mountain) since the land is closer to the sun?

Mrs. Dwyer's and Ms. Carlsons 4th grade class

Brodnicki Elementary, Justice, Ill.

Dear Brodnicki 4th graders,

Air temperatures do indeed drop with increasing elevation--about 5 degrees per thousand feet. However, at 93 million miles, the sun is so far away that even a 5.5 mile vertical trip to the top of Mt. Everest (at 29,035 feet, the world's loftiest mountain) will not take you significantly closer to the sun. We feel air temperatures as a result of air molecules bombarding our skin, and those molecules move faster when the air is warmer (and slower when it is cooler). But air pressure decreases at higher elevations and so, as air rises, the spaces between its molecules increase. This causes fewer and lower- energy bombardments on a surface (like our skin), and the air feels cooler.

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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.